This application proposes to identify and characterize glial specific proteins. In a study designed to identify novel brain specific proteins, rat brain cDNA clones were selected which corresponded to mRNAs expressed in brain but not in other tissues. One such clone (plB208) hybridized to two highly abundant rat brain mRNAs, 3200 and 1600 nucleotides in length, which were also present with a similar high abundance in rat C6 glioma cells. The nucleotide sequence of the clone was determined, providing the partial amino acid sequence of the correspondence proteins. Antibodies raised against synthetic peptides corresponding to regions of this sequence detected a 50 kd protein in astrocytes distributed throughout the brain. Preliminary evidence indicates that the cDNA clone is derived from the larger RNA species and that this mRNA probably encodes a glial specific protein of unknown structure and function, glial fibrillary acidic protein (GFAP). It is the aim of the proposed studies to: 1. Determine the complete structure of the mRNAs and protein corresponding to clone p1B208 and rigorously establish their relationship to GFAP. 2. Determine the structure of the gene encoding 1B208 and investigate the transcription of the two mRNA molecules which hybridize to p1B208. 3. Determine the time course of expression of 1B208 mRNAs and protein during development. 4. Select and characterize further cDNA clones corresponding to astrocyte specific mRNAs. 5. Select and characterize cDNA clones corresponding to mRNAs specific for oligodendrocytes and Schwann cells. These studies will generate structural and genetic information on a highly abundant glial specific molecule which we have tentatively identified as GFAP's a major brain protein which has been difficult to study because of its physical properties. Characterization of this and other glial proteins will provide a basis for determining the functions of glia, a means for classifying glia and their subtypes, and ultimately will improve our ability to understand and identify the types of glia involved in neurological disease.